1. Field of the Invention
This invention relates to lubricating oil compositions especially those containing oil-soluble wear inhibitors. More particularly, this invention relates to compositions containing at least one half-acid half-ester, half-acid half-amide, and half-acid half-thioester or certain acids and acid anhydrides, metal salts thereof, and mixtures thereof and benzotriazole or C.sub.1 -C.sub.20 alkyl substituted benzotriazole.
2. Description of the Prior Art
Anti-wear agents are intended to decrease wear of machine parts. Wear inhibitors for incorporation in motor oils and industrial oils are finding greater use as a result of greater stress placed on moving parts in high performance engines. Numerous additives have been developed for use in such oil compositions to improve the lubricating characteristics thereof and thereby to lessen the wear of the moving parts. Thus far, additives bearing some resemblance to the additives employed in the composition and method of this invention have already been used in lubricating oils. For example, certain polycarboxylic acids and derivatives thereof have been used successfully as one-component anti-rust agents in fuel oils and lubricating oils, even though they have not been used as anti-wear agents. Stromberg, U.S. Pat. No. 3,172,853 discloses a process for inhibiting the corrosion of ferrous metals in contact with corrosive media which is characterized by treating such metals with a compound having one ester group, one amide group, and two carboxylic acid groups per molecule. The molecule is formed by the reaction of two moles of an alkenyl succinic acid or an anhydride thereof and one mole of an aminoalkanol or substituted aminoalkanol. The alkenyl radical on the succinic acid portion of the molecule has from two to 32 carbon atoms.
Widmir et al., U.S. Pat. No. 3,576,743 discloses oil-soluble compositions which neutralize corrosion-causing materials in lubricants and fuels. These oil-soluble compositions are produced by reacting one equivalent of a high molecular weight polycarboxylic acid acylating agent containing a substituent having at least about thirty aliphatic carbon atoms with at least one equivalent of a polyhydric alcohol to form an ester-containing reaction mixture, which is the effective agent of the invention. This patent points out that the esterification may not go to completion: the ester-containing reaction mixture may contain acidic esters as well as some unreacted acylating agent.
Alink, U.S. pat. No. 3,762,873 discloses a process of inhibiting corrosion of metals and alloys in oxygenated and/or aqueous media which comprises adding to the media a corrosion-inhibiting amount of a substituted succinimide or derivative thereof, formed by reacting a hydrocarbon having from five to one hundred carbon atoms with a maleic anhydride or derivative thereof to yield a hydrocarbon-substituted succinic anhydride and then reacting the succinic anhydride with an amine to form an imide.
The compounds disclosed in the above patents are illustrative of one-component anti-rust agents having an oil-solubilizing group in the acyl portion of the compound rather than in, for example, the alcohol or amine portion of the molecule. The compounds disclosed in U.S. Pat. Nos. 3,183,069; 3,192,022; 2,699,427; 2,598,213; 2,908,711; and 2,977,306 are illustrative, on the other hand, of one-component anti-rust agents having an oil-solubilizing group in, for example, the amine or alcohol portion of the molecule, rather than in the acyl portion of the molecule. Udelhofen, U.S. Pat. No. 3,183,069 discloses N-aliphatic dioamic acids as rust and/or corrosion inhibitors in normally liquid oleaginous compositions. These acids correspond to the structural formula ##STR1## wherein R is an open-chain aliphatic hydrocarbon group containing from eight to 21 carbon atoms and A corresponds to the empirical formula --C.sub.2 H.sub.4 O.sub.x -- wherein x is one or two.
Gee et al., U.S. Pat. No. 3,192,022 discloses a non-lubricating, normally liquid, petroleum distillate containing a small amount, based on the weight of the distillate and sufficient to inhibit the distillate against rusting, of a succinamic acid formed by the reaction of one or two equivalents of succinic acid with one equivalent of N,N' hydrocarbon-substituted methylene diamine wherein the hydrocarbon substituents are tertiary aliphatic hydrocarbon groups, each of which contains from about ten to about thirty carbon atoms and has a tertiary carbon atom attached directly to the nitrogen atom.
Smith et al., U.S. Pat. No. 2,699,427 discloses a rust-inhibitor for mineral oils of the fuel and lubricant type having the formula ##STR2## represents the acyl residue of a dicarboxylic acid capable of forming a cyclic acid anhydride; R.sub.1 and R.sub.2 represent radicals selected from the group consisting of acyclic aliphatic radicals having at least 8 carbon atoms, cycloalkyl, aryl, alkaryl, aralkyl; R.sub.3 is selected from the group consisting of hydrogen and a radical of the same kind as R.sub.1 and R.sub.2 ; Z is selected from the group consisting of hydrogen and a salt-forming radical, and n is an integer equal to the valence of Z.
Blair, U.S. Pat. No. 2,598,213 discloses a corrosion inhibitor for use in preventing corrosion of metals which are in contact with a corrosive oil-containing medium. This inhibitor must contain at least one strongly basic amino nitrogen atom and at least one non-basic amido nitrogen atom in which the acyl radical of the amido group is derived from a higher molecular weight monocarboxy acid. However, there may be present other non-basic amido radicals derived from acids having less than 6 carbon atoms.
Halter, et al., U.S. Pat. No. 2,908,711 discloses rust inhibitors for liquid hydrocarbon compositions which are the reaction products of at least the partial amidation of itaconic acid with a diamine.
Godfrey, et al., U.S. Pat. No. 2,977,306 discloses rust inhibitors which are the reaction products of the reaction between an alphabeta dicarboxylic acid containing fewer than 6 carbon atoms and a branched chain primary amine containing at least 10 carbon atoms. A partially amidated dicarboxylic acid can then be esterified with a longchain alcohol.
Thus far, no one has discovered the simple and versatile wear-inhibiting additive composition of this invention.